Due to the thinner design of the new breed of laptops, Apple have dispensed with some of the standard ports.
Both the MacBook Air and new MacBook Pro with Retina Display have no FireWire or Ethernet port. They do have a Thunderbolt port though.
Apple has released a Thunderbolt Gigabit Ethernet adapter with plans for a Thunderbolt FireWire adapter later this year.
Unfortunately the software 1.2 update that supplied the driver for the new Thunderbolt Ethernet adapter caused serious problems. This left many Mac users with boot problems afterwards.
Apple have published a support article with advice on how to resolve these problems:
Quickly withdrawn by Apple, a new release 1.2.1 is now available:
The update is compatible with a Thunderbolt enabled Mac running OS X Lion 10.7.4.